Start with this, drag a new tab to make this, and then drag that second tab back into its origin window, leaving you with this. This is incredibly annoying behaviour, since I have to close the second window manually... and after a lot of accidental (sometimes my cpu hangs when switching tabs) dragging out of a window, it adds up. In that same vein.. Is it possible to lock tabs to a certain bar to prevent them from being dragged out? I suppose this would be an acceptable alternative, though I think both in tandem would be better than one or the other.